1. Field of the Invention
The present invention relates to a novel bisphosphite compound, a process for its production, and a process for hydroformylation of an olefinic compound employing the bisphosphite compound.
2. Discussion of Background
A process which comprises reacting an olefinic compound with water gas in the presence of a catalyst to produce aldehydes or alcohols as their hydrogenated products, is well-known as a hydroformylation process. As a catalyst for the hydroformylation reaction, it is common to use a soluble complex of an element selected from Groups 8 to 10 of the Periodic Table (hereinafter referred to as a "Group VIII metal") having an organic phosphorus compound as a ligand. In general, the ligand used together with the metal component of the catalyst gives a substantial influence to the catalytic reaction. Also in the hydroformylation reaction, it is well known that the catalytic activity and the selectivity are substantially influenced by the ligand. In order to carry out the hydroformylation reaction industrially advantageously, it is important to improve the catalytic activity and selectivity. Accordingly, various efforts to design the ligand have been made for this purpose.
Various phosphite compounds are known as a group of phosphorus compounds which may be used as the ligands for the hydroformylation reaction. In addition to simple monophosphites such as trialkyl phosphites or triarylphosphites, various phosphite compounds such as polyphosphites having a plurality of coordinating phosphorus atoms in their molecules, have been proposed. For example, JP-A-62-116587 discloses a bisphosphite compound wherein one of the two phosphite groups has a cyclic structure, and JP-A-6-184036 discloses a bisphosphite compound wherein both of the two phosphite groups have cyclic structures.
On the other hand, JP-A-5-178779 discloses a bisphosphite compound in which both of the two phosphite groups are not cyclized. In the bisphosphite compound, substituents on the bisarylene group as the crosslinking moiety are not particularly specified. As the four ester terminal groups, phenyl groups having a hydrocarbon substituent at least at the o-position, or .beta.-naphthyl groups having a hydrocarbon substituent at least at the 3-position, are used. As the hydrocarbon substituent, a bulky organic group having at least three carbon atoms such as an isopropyl group or a tertiary butyl group, is used.
As mentioned above, various phosphite compounds have been proposed as the ligands to be used for the hydroformylation reaction. However, in the hydroformylation reactions using bisphosphite compounds so far reported, the selectivity for linear aldehydes as the desired products tended to be inadequate when a high reaction rate was obtained. Reversely, the reaction rate tended to be inadequate when high selectivity for linear aldehyde was obtained.
In JP-A-6-184036 and JP-A-5-178779, the above-mentioned bisphosphite compounds are synthesized by reacting a bisarylene diol with a bisarylene chlorophosphite or a bisaryl chlorophosphite in a solvent in the presence of a nitrogen-containing base such as pyridine or triethylamine, where hydrogen chloride produced as a by-product as the reaction proceeds is captured by a nitrogen-containing base.
However, when the present inventors have attempted to prepare a group of bisphosphite compounds having bulky groups as represented by the following formulae (I) to (III), by the above method, it has been found that a monophosphite is preferentially formed, and yield of a bisphosphite compound is virtually 0.
As described in the foregoing, various phosphite compounds have been proposed as the ligands to be used for the hydroformylation reaction. However, in the hydroformylation reactions using such compounds, a high reaction rate and high selectivity for the desired product have not simultaneously been satisfied. Accordingly, there has been a concern that in commercial production, the economical efficiency will be low, and there has been a problem that such compounds are hardly useful as industrial catalysts. Therefore, it has been desired to develop a bisphosphite compound which is capable of presenting excellent selectivity for the desired product while maintaining a high reaction rate and to develop an efficient process to produce such a bisphosphite compound.